At present, when a UE (User Equipment) accesses a mobile network through an access network element, a CSG (closed subscriber group) mechanism is introduced to restrict a UE from accessing a particular access network element. In the CSG mechanism, a CSG identifies a group of UEs (or users, user). These UEs are allowed to access one or more cells of an operator, but other UEs are prevented from accessing these cells. One CSG area contains one or more cells, and all the cells contained in the CSG area are identified by one CSG ID. One CSG area is restricted to access of one group of UEs and restricts a UE other than those of this group from accessing. For one UE, CSG IDs of all CSG areas that can be accessed by the UE forms an allowed CSG list (Allowed CSG List), which can also be referred to as a CSG white list.
When the CSG mechanism is used to perform access management on a UE, access network elements accessed by the UE have three modes: an open mode, a hybrid mode, and a closed mode. When the UE seeks access through each of access network elements in the preceding three access modes, a mobility management network element obtains the allowed CSG list in user subscription data from an HSS (Home Subscriber Server, home subscriber server), and, according to the CSG ID of a cell currently accessed by the UE, an access mode of an access network element, and the allowed CSG list in the user subscription data, judges whether to allow access of the UE. Specifically, if the UE seeks access through a cell under an access network element in open mode, a network side allows access of the UE, if the UE seeks access through a cell under an access network element in hybrid mode, when resources are sufficient on the network side, the network side allows the UE to access; when resources are insufficient on the network side, the network side obtains the allowed CSG list in the user subscription data from the HSS when the UE seeks access, and judges whether the CSG ID of the cell accessed by a user is in the allowed CSG list in the user subscription data: if yes, access of the user is allowed; otherwise, access of the user is not allowed, and if the user seeks access through a cell under an access network element in closed mode, the network side judges whether the CSGID of the cell accessed by the user is in the allowed CSG list in the user subscription data: If yes, access of the user is allowed; otherwise, access of the user is not allowed.
At present, a part of the user subscription data is related to a PLMN (public land mobile network). When a UE accesses a network, a mobility management network element obtains only subscription data of a PLMN to which the mobility management network element belongs and performs access control on the user. However, when PLMN1 corresponding to a cell currently accessed by the UE is inconsistent with PLMN2 corresponding to a target cell to which the UE is to hand over, a source mobility management network element cannot perform access control on the UE.
In this case, if the source mobility management network element refuses to perform a handover in this situation, the UE can never hand over to the target cell to obtain service of the target cell. Because the handover generally occurs in a situation that the UE can no longer obtain service of a high-quality service from the current cell, if the UE cannot obtain the service of the target cell, the UE has to stay in a cell with poor service quality. As a result, many services cannot be implemented.
If the mobility management network element always allow the UE to hand over in this situation, the access control on the UE can be performed in the target cell only when the handover is completed; that is, the target cell has already allocated all bearer resources for the UE, and handover signaling interaction has already be completed. If the target network verifies that the UE cannot access the target cell, the resources already allocated for the UE will be taken back, thereby causing a waste of bearer resources; and earlier handover signaling becomes useless, thereby causing a waste of signaling resources. In addition, because the UE has already moved away from the original cell and cannot access the target cell, the UE has to perform cell reselection to find an appropriate network. In this way, a network access delay of the UE is increased, and a service cannot recover timely, which affects the user's experience.